Replacing Radiator with baseboard

We are planning to gut and rebuild our bathroom, The contractor is recommending pulling out the existing cast iron radiator (hot water system) and replacing with cast iron baseboard, which will be less obstructive in the room, i.e. we can put shelving or other storage in the area taken up by the radiator.

The amount of heat energy transferred to the room air is directly proportional to the total square inches of heat transfer surface exposed to the air.

Although modern fin tube type baseboard has a very high effeciency, due to their physical shape they will require a longer linear distance along the baseboard than what a high profile radiator would require.

All types of radiational heating devices rely upon the natural laws of nature which dictate that warm air will rise, which in turn draws cooler air near the floor towards the radiating device. In both cases their should be no furnishings or personal possessions immediately in front of the radiator which would block the natural convection current of air.

If the rest of the house of floor or zone is on the same thermostat then you must install the equivalent amount of baseboard as the radiator. By measuring the number of sections, the number of tubes in each section, the height and the type of radiator (column, thin tube slenderized, etc., multiplied by some hydronic factors and the surface area can be established which be converted to BTUs outout at tpically 180 degrees water tempertaure. That output can then be divided by 580 degrees which is what one foot of cast iron baseboard gives off, which will give the number of feet of baseboard equal to the radiator. In plain words, too many feet of baseboard and the room will be warmer, less, cooler.

The 3 rather fat columns per section have about 3.75 square feet of surface area per section. 10 sections times 3.75 = 37.50 square feet of surface area for the entire radiator. Hot water @ approx. 170 degrees will deliver 150 BTU's per square foot through cast iron, so... 37.50 times 150 = 5,625 BTU output from your radiator. If your new baseboard delivers 570 degrees per foot, then you will need 9.87 feet to equal the output from your existing radiator. If wall space is a problem, high output baseboard is available, sometimes in excess of 800 BTU's per foot requiring only 7' of baseboard.

I understand all the factoring you guys can do, and I think that's great. The only thing I'd like to add is that the lifespan of a piece of tin can baseboard in a bathroom is short, really short if you put it next to the toilet. Regardless of the length issues, cast iron baseboard or the original cast iron radiator would be my choice. If one of the walls that the new convector (remembering that baseboard is a convector, not a radiator)is on a north, west or north-west wall, it would definitely be the way to go. (Depending on the area of the country the installation is to take place).

This is just my opinion, and with it and a dollar, you can get a cup of coffee in most places.